What siege weapon did Leonardo da Vinci design using a spring-powered catapult mechanism?

Leonardo da Vinci designed a spring catapult using a mechanical launching mechanism.

His military notebooks contain studies of projectile machines that used stored energy to hurl stones or other missiles. In a spring catapult, a bent or tensioned element stores energy and releases it when the throwing arm is triggered. Leonardo examined the geometry of the arm, the strength of materials, and methods for winding or resetting the machine.

These studies belong to a long tradition of siege engineering, but Leonardo applied Renaissance interest in mechanical analysis to older weapon types. His drawings often show alternative arrangements rather than one finalized model, so the exact dimensions and performance of any single catapult design should not be assumed.

A catapult is a broad category of projectile machine. A trebuchet uses a counterweight, while a spring catapult stores energy elastically. That distinction matters because Leonardo also studied several other siege devices, and not every drawing labeled a catapult used the same mechanism.